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EMA'BSON E. MAIN, 0F INDIANAPOLIS, INDIANA.

. SPARK-PLUG.

Specification of Letters Patent. I Patented June 3, 1919.

Application filed May 15, 1918. Serial No. 284,669.

To all whom it may concern:

Be it known that I, EMARSON E. MAIN, a

citizen of the United States residing at Indianapolis, in the county of Marion and State of Indiana, have invented a new and useful Spark-Plug, of which the following is a specification, reference being had to the accompanying drawings and to the letters and figures of reference marked thereon.

This invention relates to a device that is used in connection with an explosion engine as one of the elements of the ignition systems thereof wherewith a jump sparkis obtained forigniting the fuel or explosive mixture to actuate the engine, the invention having reference more particularly to a spark plug that is designed more especially for use in connection with the hi her power explosion engines having Stan ard silzes of sockets or holes to receive the spark p ugs.

An object of the invention is to provide a spark plug of the above-mentioned character that shall be so constructed as to afford the maximum sparking capacity within the range of'the standard size adopted for sparkplugs.

Another object is to provide an improved spark plug which shall be so constructed-as to be reliable in operation and not be liable to becomederanged or damaged either in handling or in use.

A further object is to provide improved electrodes in spark plugs which shall not be liable to deteriorate or become unreliable 'because of carbon deposits thereon.

to the minimum in order to insure reliability ndq'naximum efiiciendy and also long life of tlf spark plug.

t :e above-mentioned and other obects in view the inventionconsists in inrto keep the temperature of the spark p ug down structed substantially in accordance with the invention; Fig. 2 is a section on the line IIII in Fig. 1; Fig.3 is a bottom plan of the spark-plug; Fig. 4 is a section of parts separate from the other parts of the spark plug; and Fig. 5 is a fragmentary reproduction of aportion of Fig. 2 on an enlarged scale.

Similar reference characters on the different figures of the drawings indicate like parts or features of construction herein-' after referred to in detail.

On the drawings the numeral 1 indicates the metallic body or shell of the improved spark plug and it has a shank 2 on one end thereof which may be of the adopted standard external dimensions to enter the aperture with which the explosion engine is usually provided. The normal upper portion of the body has a chamber 3 therein from which a bore 4: extends through the bod and into the shank, the lower portion of the shank having a relatively smaller bore 5 communicating with the bore so that the body is hollow throughout. The shank has the ,usual external screw threads 6 thereon whereby to secure the body in lace. The shank has a continuous beveled ace 7 therein extending from the bore 5 and flaring outward to the end of the shank and thisconstitutes an annular negative or side. electrode which affords a very wide pole or point at which the jump spark may be produced at any point along the length of the electrode surface, and therefore in case one point is obstructed or for any reason rendered inefficient the spark may occur at another point.

j'ohainber;'iand a washer'or g'asketl'l is 'arprovements in a spark plug generally an moreiparticularly in. novel electrodes and also in" a. feature .wher'e'by cool the spark plug; andythe invention consistsfl'also fur-' ther lnlthe' novel parts, and the comb'm'a- J" I tions and arrangements of parts, as he inafter particularly described. and further 'de-' fined. 1n fthe, acc'ompanyin .,claiins. A

Referring to the drawln'gs Fi l is "a" side elevation of the spark p ug'co'n' ranged u on the "outer 'endportion of the collar'an engaged bya o v ofa pressed down or spunportion "if i t e be or shell o s u e e in ul tor.

place.

he insulator orf core has af'nec'k ortioii x nd n dow rd nfo, i

re 4. The core 8jhas' 'a bore o'r chann .t ex e ng t r th hi e fil'infi i h L. ltlir ing 6 f n t' w h ma mf-jzlessextentiAg tondn tin" St mj... 1

16 is arranged "in-magnet s through -'the'- bore 14: and has external screw threads 17 extending from one end thereof, some of the screw threads being-in the bore 14 and embedded in the cement for securing the stem to the, core; and, in some cases the stem may have a collar 18 thereon engaging the end of the neck 13 of the core. Preferably a nut 19 or facing washer is arranged on the stem '16 and seated on the top of the core-8, a terminal nut 20 being seated on the nutor washer 19. The nut has a bore 21 receivingthe upper end of the stem 16'and provided with screw threads 22engaging thescrew threads 17, the nut preferably having a relatively smaller aperture 23 extending through it from the bore. The nut has a circumferential groove 24 therein to receive the, standard snap terminal whereby to connect a circuit wire to the nut and thereby with the stem 16.

. A novel positive or center electrode 25 is provided which is disk-shaped and arranged within the annular side electrode 7 the top 26 of the positive electrode being convex and integrally connected to the lower or inner end of the stem 16, the peripheral edge 27 of the positive electrode being greater in diameter than the bore 5 of the shank and arranged adjacent to but separate from the larger outer portion of.

the annular electrode 7, so that an improved annular gap is provided between the two electrodes and permitting a jump spark to be roduced at any portion of-the gap.

he center electrode 25 preferably has apertures 28, 28 therein to permit free passage of air or gases and also to permit oil to readily flow down from the interior or bore of the shank'2 in case oil is received into the shank.

The lower or outer face .of the disk is referably made flat and in practice it has een found that the best results are obtained .the disk completely removing any accumulations. The substantially flat face of the disk will also aid in keeping the plug free of carbon for the reason that when the said face becomes heated any oil thrown into contact therewith will be immediately thrown off inasmuch as the flat face does not pro-- vide an opportunity for lod'gment.

For the purpose of cooling the center electrode or keeping itstemperature down to the minimum degree, a cooli system therefor is provided and preferab y is associatedably havinga suitable closure 31in its-upper portion; and, the opening 23 in' thenut 20 preferably has a suitable closure 32 therein.

In practical use the electrical current is conducted by the conducting stem 16 to the center or positive electrode 25 and is discharged across the gap between the edge 27 and the face or edge 7, resulting in a jum spark which is full and'strong as require to reliably ignite the explosive charge in the engine cylinder. The advantages of the large jump spark for high power engines and consequent relative gain in eificiency is well understood and results from the novel construction and relative arrangement of the electrodes. Carbon deposits are prevented by explosions in the hollow shank. The. heat generated by the explosions causes air to circulate in the bore 29 of the conducting stem in case the bore is open to the atmosphere which it may be in some cases, resulting in the center electrode being prevented from becoming excessively hot. In case the liquid 30'be present in the bore 29 the heat causes the liquid to expand and rise in the bore, so that the heat is carried upward to the cooler upper portion of the stem and the insulator, the cooled liquid being repeatedly condensed anddescending to re eat the process.

aving thus described the invention, what is claimed as new is 1. In a spark plug comprising a shell threaded uponits exterior and constituting one electrode, an insulating member arranged within said shell, a stem extending through said insulating member and terminating in a disk, the lower or outer face of which is flat, the inner face thereof being a shallow cone, said disk' having a plurality of apertures therein, the perlphery of said disk being spaced from the lower inner edges of the shell, and means for positioning the stem within the insulating member.

2. A spark plug comprising a shell and constitutmg one electrode, an insulating member arranged within said shell, a stem extending through said insulating member and terminating in a disk, the lower outer face of which is flat, the inner face of which is slightly coned, said disk being concentrically spaced within the inner edges of the shell end and provided with a plurality of openmgs;

3. In a spark plug, the combination of a shell With an externally-threaded shank having a bore therein that has an outwardly-flaring orifice, a hollow insulating core secured in said shell, a hollow conducting stem secured in and extending through said core, a disk fixed on one end of saidstem and having its peripheral edge located opposite and closely adjacent to the larger outer portion of said flaring orifice, the center of said disk being a closure to one and covering said plug.

In testimony whereof, I aflix my signature 1n presence of two Witnesses.

EMARSON MAIN.

Witnesses:

E. T; SILvIUs, F. M. ROEDER. 

